Latex emulsions of resins may be produced using PIE processes in which resins are dissolved in a mixture of water, optionally a base, and one or more organic solvents (e.g., methyl ethyl ketone (MEK), isopropyl alcohol (IPA) or both) to form a water-in-oil (W/O) dispersion (i.e., water droplets dispersed in continuous oil phase). Subsequently, water is added to convert the dispersion into an oil-in-water (O/W) dispersion. In embodiments, liquids from a prior PIE can be reused in a subsequent PIE.
Amorphous polyester latexes may be produced in a solvent reuse process with organic distillate from a previous PIE. The solvent(s), such as, MEK and IPA, from a latex emulsion can be distilled under vacuum and then used to dissolve resin in a subsequent PIE. Solvent reuse processes provide savings in raw material, solvents(s), cost and solvent disposal fees, leading to significant reduction of latex production cost. When IPA is used as a solvent, particle size of amorphous resins can correlate to amount of IPA.
When ammonium hydroxide or ammonia is used as base, the amount of ammonium hydroxide or ammonia can impact neutralization ratio of crystalline polyester resins and resin particle size. However, the acid number of crystalline resins vary. Thus, for crystalline polyester resin PIE, where an objective is to employ solvent reuse and to avoid solvent disposal fees, base amounts must be considered and carefully controlled to control latex particle size from lot to lot.